signals via PR on hESCs. (a) hESCs treated ± P4 (2 μM), RU-486 (20 μM), and/or appropriate controls for 5 days were collected, and equal amounts of protein from cell lysates were analyzed by immunoblot for PR-A with anti-human PR rabbit polyclonal antibody (C-19) generated against the C-terminus, β-actin antibody and GAPDH antibody [11, 18]. EBs were treated ± RU-486 (20 μM) and analyzed for these proteins. (b) hESCs were treated with and without P4 (2 μM) or RU-486 (20 μM) or both for 5 days and analyzed with immunoblot for StAR, β-actin, and GAPDH. Molecular-weight markers are shown on the left of immunoblots.